1. Field of the Invention
This invention relates to processes and apparatuses for the cleaning of contaminated gases, to processes and apparatuses for ionizing gases or charging particles in fluid streams, and to processes and apparatuses for increasing the efficiency of wire-plate ionizers.
2. Description of the Prior Art
Many industrial processes discharge considerable amounts of atmospheric contaminants as particulates in the sub-micron range. This type of particulate is most difficult to control. Fine particulate emission is becoming a major source of air pollution as the larger particulate problems have been easier to bring under control.
Curently, there are three basic approaches to the problem of handling sub-micron sized particulates in contaminated gases. The first approach is the traditional electrostatic precipitator system. The application of electrostatic precipitators to fine particulate control has several inherent problems.
The second basic type of cleaning system is the wet scrubbing approach. The wet scrubbing approach as applied to the control of fine particulates generally is of the high-energy venturi type. In order to capture the sub-micron particulates in water droplets, large quantities of water must be injected and high relative velocities employed. Both of these factors increase the pressure drop of the system, and operating cost is directly related to this pressure drop.
The third basic type is generally referred to as the dry filter system. A problem with equipment of this type, however, is the temperature limitation of the filter elements, and the related problem of the high cost of reducing this temperature.
Efforts have been made to improve the efficiency of these various techniques by electrostatically precharging the contaminants upstream of the primary collecting system. These efforts have generally been unsuccessful due primarily to the lack of an effective mechanism to produce a continuous, sufficiently intense field to adequately charge and affect the sub-micron sized particles.
Ionizers for charging particles or ionizing gases have heretofore been of the wire-cylinder, wire-plate or needle point type and have been limited to field intensities of about 10 kv/cm average field and low ion density limits of about 10.sup.9 ions/cm.sup.3 in the interelectrode region. As a result, the usefulness and effectiveness of such ionizers have been limited.